Anticomplementary activity of Fusobacterium polymorphum in normal and C4-deficient sources of guinea pig complement

Fusobacterium polymorphum has been isolated from the gingival crevice in humans and has been implicated in the immunopathology of periodontal diseases. The presence of alternative complement pathway factors in gingival crevice material suggests the contribution of this process in the manifestation of the local host response. A complement consumption assay was used to show that the anticomplementary activity of a cell-wall preparation from F. polymorphum in guinea pig complement progressed optimally at 37 degrees C and suboptimally at 0 degrees C. Similar levels of complement consumption were recorded at both temperatures, but a higher concentration of cell walls was required to demonstrate maximum activity in the cold. Augmentation experiments with additional normal and heat-treated complement showed the presence of heat-labile factors that controlled and limited the consumption of complement to a constant proportion of the total amount present. These same experiments indicated that there were no reactive antibodies in the complement used in the assay. Similar tests with C4-deficient guinea pig sera confirmed that F. polymorphum cell walls were capable of generating alternative complement pathway activity in guinea pig sera.